In 2002, Colorado DOT placed both concrete and asphalt on Powers Boulevard in Colorado Springs to determine the pros and cons of each pavement while each is exposed to the same weather, soil, and traffic conditions. The northbound side is concrete (right); southbound is asphalt. The study should be completed within the next five years. Photo: Gregg Gargan, CDOT
The life-cycle analysis debate
PCA's Sullivan, however, argues that concrete is still the most cost-effective choice. He cites “flawed” life-cycle cost analysis calculations that use the same discount rate for expected concrete and asphalt cost increases — even though concrete costs have risen slower than asphalt — thereby underestimating concrete's long-term cost advantage.
The National Asphalt Pavement Association (NAPA) disagrees, taking issue with supporting research that was funded by PCA and other concrete associations through Massachusetts Institute of Technology's (MIT) Concrete Sustainability Hub.
NAPA has published Special Report 203, Material-Specific Discount Rate: Inappropriate for Life-Cycle Cost Analysis, which supports current DOT and Federal Highway Administration life-cycle cost procedures. The report attempts to discredit MIT's proposed material-specific discount rate that is based on historical price data and varying inflation rates.
NAPA fears the research could influence federal legislation. For instance, in February the House passed the Civilian Property Realignment Act (H.R. 1734), which includes an amendment to require life-cycle cost analysis of at least 50 years on all federal building projects costing more than $1 million. The bill could open the door for mandated life-cycle cost analysis procedures — possibly including a material-specific discount rate — on all publicly funded projects, including roads and bridges.
“[We oppose] asking Congress to mandate a life-cycle cost procedure which is not accepted by economists and which tilts the playing field in favor of one construction material,” says Mike Acott, NAPA president. His association calls the material-specific discount rate a “computational work-around” that skews life-cycle cost analyses for construction materials, including asphalt, concrete, steel, wood, and plastics.
Ultimately, both camps agree that sustainability is an economically responsible choice. Ed Sullivan includes green building in his list of growth areas for the concrete industry. He predicts green building practices such as using recycled materials “will continue to grow not only because it's the right thing to do, but because it makes economic sense.”
Likewise, “cost has been the major driver of adopting green techniques” in the asphalt industry, according to Jon Epps PhD, PE, executive associate director of the Texas Transportation Institute.
Epps encourages looking at the “triple bottom line” of economic, social, and environmental impacts to determine the best paving solutions — a message that could ultimately save our infrastructure, regardless of the paving materials we choose.